1. Technical Field
This invention relates to apparatus and methods for re-shaping the backing plates of rotary drum brake cores in the making of re-manufactured brake shoes.
2. Related Prior Art
Rotary drum-type brake shoes are formed by bonding a lining of friction material such as asbestos or the like to the convex outer surface of a metal backing plate of the brake core. Extending from the opposite concave inner surface of the backing plate are a set of laterally spaced mounting brackets for securing the shoes to the associated calipers of the brake system.
Over time, the lining is caused to wear to the point where the brake shoes need to be replaced. It is quite common to reclaim the metal core of spent brake shoes and use them to produce remanufactured brake shoes. The remanufacturing process involves stripping the old liner from the core, reshaping the backing plate to correct any warpage that may have occurred in service from prolonged exposure to extreme temperature changes and high pressure conditions, and applying a new lining to the reshaped core.
Presently, the backing plates are reshaped via a coining operation in which the convex outer surface of the backing plate is cradled by complementary concave working surface of a fixed lower die of a coining press. An upper movable die of the press supports a pair of die inserts or tools having lower convex working surfaces that compliment the concave inner surface of the backing plate. The die inserts are spaced laterally from one another by a distance sufficient to straddle the mounting brackets of the core. In operation, the backing plate is struck with great force by the upper die inserts, causing the side regions of the backing plate to either side of the mounting brackets to be reshaped to the proper configuration.
One inherent disadvantage of the present tooling and reshaping process is that the middle region of the backing plate located between the mounting brackets is not acted upon by the tooling and thus does not get reshaped in the process. Consequently, there is no assurance that the middle region of the backing plate is true to shape following the current coining operation.